Serena Van Dyke can't foresee a day when she will give up one of her two jobs.

The 27-year-old works full time as an ambulance dispatcher and part time as an emergency medical technician. She works seven days a week, no days off. She barely makes ends meet.

"I have to have both jobs," she said, "just to pay for groceries, gas and everything else."

Van Dyke isn't the only one. Since the recession started, more people are moonlighting — working a full-time job plus another job — to pay for necessities or to hedge against possible layoffs and pay cuts. Consider:

Twelve percent of workers plan to take a second job this year, according to a survey by CareerBuilder.com.

That's up from single digits during the first half of the decade, before the economic downturn, CareerBuilder.com reported.

The reason is almost always economic. According to the Bureau of Labor Statistics, the number of U.S. residents who said they had two jobs because of tight financial times was 7.3 million in 2010, up from 4.5 million in 2007, the year the recession began.

Van Dyke, who lives in Ripon, doesn't need numbers to tell her times are tough. She started working a second job to pay her way through paramedic school and has since found she needs both paychecks to cover student loans as well as the rising cost of essentials, such as food and gas.